Public trust in politics is at a low ebb, our Guardian-ICM poll said last week. Most people are angry, not apathetic, and what makes them angriest is politicians who break their promises, which should be no surprise. In living memory there has been no greater deception than in the rift between this government's pre-election words and post-election deeds.

Nick Clegg gets most blame over tuition fees, a promise that won university seats and then betrayed so many fresh first-time voters. But David Cameron wins the mendacity prize by what he might call a country mile.

He pledged no rise in VAT; it rose immediately. On child benefit the prime minister said, "I wouldn't means test it", but he did. The education maintenance allowance would stay; it went. Vote blue, go green, became "get rid of all the green crap". Days before the election, Cameron said any minister proposing a frontline cut would be "sent straight back to their department to go away and think again".

Yet 6,000 nurses, 10,000 police officers and 10,000 teachers have gone, along with libraries, swimming pools and much care for the elderly. Cameron's posters said no NHS cuts – but that was a sleight of hand, since the NHS needs 3% just to stand still, so A&E is spilling over. "No top-down reorganisation" turned into £3bn of NHS turmoil.

Some accepted deficit reduction as an excuse – but it has corroded trust. Why should anyone believe a word any party says next time? What words are left untarnished when Cameron's "compassionate conservatism" and "big society" used them all up?

New Labour shares much of the blame, the disgraceful Iraq dossier its most egregious dishonesty. Spin often burnished their results and hyperbolic "world class" or "world-beating" boasts took the shine off genuine achievements. Yet Labour's 1997 five pledges were control-freak cautious, as the party was nailed to every promise by a hostile press, while Cameron's cavalier vows faced virtually no scrutiny.

Ed Miliband has wisely said he will under-promise and hope to over-deliver. Too much silver-tongued oratory risks disappointment – ask Barack Obama. Trust might be restored with a modest aim for steady improvement – yet perversely we crave political inspiration too, vision and hope with roses and circuses to leaven the daily bread of politics.

Intense mistrust of parties is growing dangerously with each generation: with fewer than 1% of the population members of a political party, people understand less about the necessary compromises. Our poll's "angry" voters say they want politicians to say what they believe, not mouth the party line-to-take. Too many MPs are pitifully thin on vocabulary and imagery, short on wit, warmth, passion or imagination. Some exceptions – the TUC's Frances O'Grady, Kenneth Clark, Shirley Williams – have the gift of sounding like themselves, as if they believe what they say. Put the journalist Owen Jones on a platform and he blows your socks off. The public trusts Margaret Hodge's authentic passion on tax-dodging companies, though Boris Johnson and Nigel Farage suggest verbal felicity can be an actor's knack, not proof of honesty. Authenticity – or a semblance of it – is rare political gold dust.

But don't forget that politicians speak robotically for a reason – and voters share the blame. Voters say they dislike party discipline, wanting MPs to speak their consciences, yet as every original thought becomes a newsworthy "gaffe" and "split", voters also punish parties severely for any sign of disunity. Voters are contrary. If they want more electoral choice, why did they reject a small improvement in the AV referendum? They say they want honesty, but they don't always reward it.

The truth is that taxes must rise: as the Institute for Fiscal Studies says, the £43bn cuts projected after the election are politically and practically impossible – and both parties know it. But watch the Tories run a "double whammy" campaign against Labour, knowing full well they too will raise tax. Dare Labour say yes, we'll raise income tax; Gordon Brown should never have cut the basic rate by 3p? Or, if you want the NHS secured, national insurance should rise by 2p: you get what you pay for. Voters may pretend to like honesty, but they are still inclined to back whoever pretends they can do "more for less" – Swedish services on US taxes. Trust comes with conviction and, as Steve Richards wrote on these pages yesterday, the more Ed Miliband follows his beliefs, the better he does. Labour might try reminding people that tax is the price paid for civilisation – but dare they trust the voters to reward such honesty?

Nor will Cameron and Osborne dare to be honest about their true intent at the next election. If the Tories won they would reduce the state to a rump, dismantle the NHS as a provider, shrink the BBC to a minor player, privatise schools, let the rich keep more, and other unpopular policies they will certainly disguise at election time. If Cameron swears none of that will happen, why believe him?

But voters are shifty too. They want outspoken MPs – yet they want party unity. They want honesty – but they rarely vote for it. Ben Page of Ipsos Mori says that people know that politics requires low cunning: "They choose the most capable, best in a crisis, not the most honest." He is more sanguine about trust in politics: it has always been rock bottom, very rarely reaching 20%. Even in wartime, Gallup found few people trusted politicians to act in the national interest. Don't panic about turnout, he advises: it rose in 2010. Voters turn out for something worth voting for, and in marginals where their vote counts.

On the doorstep, no candidate dare wag a finger to remind these angry citizens that they have duties too. No one tells them they should inform themselves better on things they care about, with reliable facts at a click of a mouse. Who dares tell them that complaining is no use if they take no part in the democracy that rules their life? Russell Brand nihilism is not OK – and where is he now? Is he out there doing something – anything at all, protesting, rioting – organising or still not arsed? In the end it's the arsed who keep any kind of democracy going – and the rest should zip their lip unless they are ready to get off their arses now and then. Don't get angry, get even. But brave would be the vote-wooing politician who dared give voters back a bit of their own medicine on the doorstep.